Various abbreviations that appear in the specification and/or in the drawing figures are defined as follows:
3GPPthird generation partnership projectUTRANuniversal terrestrial radio access networkNode Bbase stationUEuser equipmentEUTRANevolved UTRANaGWaccess gatewayeNBEUTRAN Node B (evolved Node B)PRBphysical resource blockNPRBnumber of PRBsLTElong term evolutionBWbandwidthCQIchannel quality indicatorFDMAfrequency division multiple accessOFDMOrthogonal Frequency Domain MultiplexPSpacket schedulerLAlink adaptationFDPSfrequency domain packet schedulerSC-FDMAsingle carrier FDMAULuplink (UE to eNB)DLdownlink (eNB to UE)MIMOmultiple input, multiple output
The exemplary embodiments of the invention described herein relate generally to wireless communication systems that apply OFDMA in the downlink, where a UE may be freely allocated to frequency bands or sub-bands. One exemplary, but non-limiting type of such a wireless communication system is the LTE of 3GPP, also known as EUTRAN. The current working assumption in 3GPP is that the DL access technique will be OFDM, which will create an opportunity to perform link adaptation and user multiplexing in the frequency domain. The UL access technique will be SC-FDMA.
In order to be able to perform adaptation in the frequency domain, it is important that the PS and LA units in the Node B have knowledge of the instantaneous channel quality. This knowledge is obtained through the signaling of CQI reports from the different UEs served by the Node B. Several approaches for defining the CQI contents (what is actually signaled) have been discussed in 3GPP. Common to many of these approaches (e.g., single-stream and MIMO CQI methods) is that the UE indicates its best PRBs out of all the available PRBs. Examples of this approach have been referred to as ‘best-M’ and ‘threshold CQI’.
However, as the possible number of best PRBs out of a total number of PRBs to be reported increases, the resulting permutation space grows dramatically. As this permutation space grows, the number of distinct signalling values also increases, thereby placing significant processing, memory storage and signaling burdens on both the UE and Node B CQI reporting mechanisms.
Reference with regard to aspects of the foregoing description of CQI reporting can be made to 3GPP TR 25.814, V1.5.0 (2006-05), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved UTRA (Release 7), generally pages 1-22 as well as pages 47-49, which include Sections 7.1.3.1.1.1 “Channel Quality Measurements” and 7.1.3.1.1.1.1 “Channel Quality Indicator”.
Reference may also be had to: 3GPP TSG RAN WG1 RAN meeting #47, Riga, Latvia, 6-10 Nov., 2006, R1-063086, “Overhead reduction of Best-M based CQI reporting”, Huawei, as well as to 3GPP TSG RAN WG1 RAN meeting #47, Riga, Latvia, 6-10 Nov., 2006, R1-063094, “Comparison of CQI feedback schemes”, Mitsubishi Electric.
Reference may also be made to 3GPP TSG-RAN WG1 Meeting #48, St. Louis, USA, 12-16 Feb. 2007, R1-070873, “Signaling Resource Allocations in DL Control Channel”, Alcatel-Lucent.